The present invention relates to a charging device for an electrostatic copying machine, particularly of the type facing a circumferential surface of a photo-sensitive drum or a transfer paper or the like so as to charge the photosensitive surface.
In FIG. 1 is i11ustrated a schematic arrangement of a conventional type of an electrostatic copying machine. In this figure, a light from source 2 is reflected by an original 3, and its image is projected onto a photo-sensitive drum 1 through an optical system including mirrors 4, 5 and lens 6. Toner powders in toner box 7 are fed to a developing unit 8 adjacent to the drum 1, and a transfer paper 9 is supplied to a circumferential surface of the drum 1 through a paper feeding mechanism. Around the circumferential surface of the drum 1 are respectively arranged a first charging device 10 for charging the drum in advance, a second charging device 11 for transferring an electrostatic latent image stored on the surface of the drum onto the transfer paper 9, and a third charging device 12 for separating toner powders from the drum. The transfer paper 9 having a toner image transferred thereon is passed through a fixing unit 13 and discharged on a take-up tray 14.
The charging devices 10 to 12 are constructed so that a charging wire, energized by a high voltage, is arranged in a case. This arrangement exhibits some disadvantages, in that toner powders are apt to be adhered to the wire during operation. The discharging performance of the wire with respect to the drum 1 is decreased and a re-adhering of toner powder to the drum 1 or a hazardous adhering of toner powder to the transfer paper 9 occurs. As a further disadvantage, a cleaning is required generally for every 2,000 hours of operation.
In view of the above-mentioned disadvantages, it is a main object of the present invention to provide a charging device for an electrostatic copying machine, in which a piezoelectric vibratory element is arranged so as to apply a vibratory motion for a specified duration of time to a charging wire for use in charging a photosensitive drum or a transfer paper or the like, and thereby prevent any adhesion of toner powders to the charging wire.
Referring now to the following detailed description and accompanying drawings, several preferred embodiments of a charging device for an electrostatic copying machine constructed in accordance with the present invention will be given to aid in a more complete understanding of the invention.